MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 17 
gneiss, and the ore, through successive stages, to magnetite’ (p. 80). 
The structure of the ore body is very well described and the paper 
is well illustrated with diagrams of horizontal and vertical sections 
of the ore body at different levels of the mine. 
It was during this period that Williams *° began his now famous 
petrographic studies of the rocks near Peekskill which were earlier 
called the Cortlandt series by Dana. Williams proved conclusively 
the igneous origin of these rocks and in his final paper *° gave a 
carefully illustrated and convincing account of the contact- 
metamorphism produced in the adjoining schists and limestones by 
the intrusion of the massive igneous rocks. 
During the field work of the New Jersey survey in 1885, Doctor 
Britton found what appeared to be an extension of the Cortlandt 
series on the west side of the Hudson river, not far from Stony 
Point. This was later brought to the attention of J. F. Kemp,” 
who studied this occurrence and connected the rocks with the 
eruptives on the east side of the river. Doctor Britton extended his 
field work into southeastern New York as an aid to a better under- 
standing of his problem in the New Jersey Highlands. As a result 
of his studies he concluded that the micaceous schists and 
crystalline limestones of Westchester county were incorrectly 
classified by Dana as the metamorphosed equivalents of Cambro- 
Ordovician sediments, for, in a paper which appeared in the School 
of Mines Quarterly * this very definite statement appears: ‘‘ There 
are doubtless some basins of more or less altered Paleozoic rocks 
in the northern part of the county (Westchester), but by far the 
greater portion of the rocks are unquestionably Upper Archean.” 
(p. 38) Merrill, who was associated with Doctor Britton in the 
study of the rocks of the New Jersey Highlands and in the pre- 
liminary examination of the Hudson River section, subsequently 
made a more extended study of the latter, corroborated the general 
results of Doctor Britton’s work in New Jersey, but took issue 
with him on the age of the crystalline limestones and schists of 
Putnam, Westchester and New York counties. While Merrill 2° 
25 Williams, G. H. Amer. Jour. Sci., 3d ser. 31: 26-41, 1886; 33: 135-43, 
and 191-99, 1887; 35: 438-48, 1888; 36: 254-69. 1888. 
76 Op. cit., 36, p. 254-69. 1888 
27 Kemp, J. F. On the Rosetown Extension of the Cortlandt Series. Amer. 
Jour. Sci., 3d ser., 36: 247-53. 1888. 
28 Britton, N. L. On Recent Field Work in the Archean Areas of 
Northern New Jersey and Southeastern New York. School of Mines Quar- 
terly, 9: 33-39. 1887-88. 
29 Merrill, F. J. zd On the Metamorphic Strata of Southeastern New York. 
Amer. Jour. Sci., 3d ser., 39: 382-92. 1890. 
